The present invention relates to a device for controlled dispensing of liquid and, more particularly, a blood serum filter dispenser having an arrangement for storing and dispensing the filtered serum with the minimum possibility of contamination.
Because of the infectious diseases, including the HIV virus, that can be transferred via blood serum, medical laboratory personnel are greatly concerned about the possibility of contamination. The ordinary procedure used in clinical laboratories in the testing of blood are: (1) a capped collection tube containing blood is centrifuged to cause the red cells to separate from the serum and settle into the bottom of the tube; (2) the cap is removed from the tube, and a smaller, filter tube having a filter covering the leading end is pushed in the manner of a piston down the collection tube, forcing the serum in the collection tube through the filter into the filter tube; and (3) either the serum is poured out of the filter tube into small cups or other tubes for testing, or a pipet is inserted into the filter tube and serum is withdrawn and then dispensed into the small cups or other tubes.
There are a number of opportunities for contamination to occur during the foregoing procedure: (1) When the filter tube is pushed down into the serum in the collection tube, serum is forced through the pores of the filter at a high velocity. This provides the possibility, at the moment that the serum first emerges from the filter, for aerosoling, that is, the formation and expulsion into the air of small droplets of serum. These droplets can fly up into the face of laboratory personnel as a contaminate. (2) The serum left in the smaller tube is subject to spilling if the tube is accidentally tipped over. (3) The dispensing pipet is one more contaminated item that must be discarded after each test. (4) Serum poured from the filter tube is subject to spilling and uncontrolled dispensing. (5) Pipets might drip when moved from the smaller tube to the small cups or other tubes. (6) Serum must be capped or covered during storage. The cap or cover is another item that becomes contaminated and must be disposed of.
It is sometimes convenient to store the serum with the red blood cell clot in the tube after centrifuging. A problem with this is that some chemistry values will change (for example, glucose and potassium values will increase) and incorrect analysis will result. In order to prevent this, sometimes the serum is poured off and sometimes a mechanical barrier is placed between the clot and the serum.